Method

1. For the crystallised mint leaves, lightly beat the egg white. Sprinkle half the sugar over a lined baking tray. Dip the mint leaves in the egg white and place on the sugar. Sprinkle over the remaining sugar. Pick each mint leaf up from its tip and shake off any excess sugar. Put on a wire rack and leave to dry out for several hours, preferably overnight. Store in an airtight container to keep fresh.

2. To make the dough, sieve the flour and icing sugar into a large mixing bowl. Add a pinch of salt and the lemon zest. Make a well in the middle. Lightly whisk the egg with the sour cream and two tablespoons water. Pour into the well.

3. Using a fork, start working the flour into the wet ingredients, until you have a rough, floury dough. Turn the whole lot out on to a work surface and knead until the dough is smooth. It should not be sticky – if it is, add a little more flour. Cover the dough with clingfilm and leave for 1 hour.

4. When you are ready to make the pierogi, roll out the dough to a thickness of between 1-2mm. Cut out rounds of 8cm/3½in diameter, bring the offcuts of the dough together to make the remaining circles.

5. Toss the blueberries in the sugar just before you need to use them – you don’t want them to start to macerate and give out juices. Put 4-5 blueberries on each pastry round in a line, then bring the edges together to form a crescent shape. Crimp or pleat together with your fingers or use a fork to seal.

6. Bring a large pot of water to the boil. Cook the pierogi a few at a time, they are ready when they float to the top, this should take about 2-3 minutes.

7. Melt the knob of butter in a large frying pan and add one teaspoon caster sugar and a pinch of cinnamon. Once melted, add the pierogi, in batches, and fry for a couple of minutes on each side until starting to crisp up and brown.

8. Sweeten the sour cream by whisking in the icing sugar.

9. Serve the dumplings with the sweetened sour cream, crystallised mint leaves and a sprinkling of icing sugar.